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Supercell Drops Baseball-Sized Hail

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One of the worst storms to strike central West Virginia dropped nearly 3″ diameter hail, caused extensive wind damage, and caused flash flooding during the afternoon of August 30th, 2006, and was classified as a supercell.

Though fairly uncommon in our area compared to the rest of the United States, supercells have occurred in our region in the past, some of which causing extensive damage. A supercell is essentially a severe thunderstorm with a deeper rotating updraft.

Supercells are a weather phenomenon uncommon to our area, but they can occur here in West Virginia. This supercell in Kansas caused extensive damage. Photo courtesy WIBW TV.

Setup

The surface map for the morning of August 30th, 2006 showed a low pressure system in North Carolina, with a cold front extending down to the Gulf of Mexico. A secondary and much weaker front existed from New England down into the Ohio River Valley. With the two fronts present, very little sunshine appeared in the sky during this day.

Despite the lack of sunshine, there was some elevated amounts of wind shear in our area during the afternoon. Wind shear means that winds are blowing from different directions at different heights. Wind shear not only aids significantly in creating the supercell, but it also allows the storm to be tilted, which is important for maintaining a separate updraft and downdraft region for the rogue storm to survive with (it essentially needs these two attributes for the storm to survive and wind shear allows that).

The surface map from the morning of August 30th didn’t indicate a severe weather episode. However, despite the setup, one large supercell was able to form thanks to elevated wind shear.

The visible satellite (top left) indicated very little in the way of sunshine during the afternoon of the 30th. CAPE, which is a way of looking at the amount of energy available for storms in the atmosphere, was very low in our region (top right). The supercell composite, a derived product to determine the favorability of supercells in an area, was also very low in our region that afternoon (bottom left). However, elevated amounts of wind shear (bottom right) was present that afternoon across our entire area. Once a thunderstorm flared up in eastern Kentucky, it tapped into that wind shear, and would cause significant damage to some areas of central West Virginia.

The Supercell on Radar, August 30th, 2006

The storm first began to take shape around 12:30 p.m. in Boyd and Carter Counties in Kentucky, dropping heavy rainfall in that area. Trees were also reported down in that region.

By around 1:15 p.m., the storm moved into West Virginia, knocking trees down in Wayne and Cabell Counties. Cabell County also saw high water issues as a result of the storm.

The storm followed along I-64 through Cabell and Putnam Counties, before moving into Kanawha County. At around 3 p.m., the storm moved into the county, which is when the supercell began to strengthen significantly in intensity. Wind damage reports were received in western Kanawha County. Some schools in Kanawha County dismissed a half hour early in anticipation of the storm.

The storm reached its peak stage as it moved into eastern Kanawha County. Extremely large hail, flash flooding, and damaging wind gusts in excess of 70 mph all were recorded in this storm as it moved past Charleston and into the eastern side of the county.

Doppler radar base reflectivity (top left) shows the storm at its peak intensity in eastern Kanawha County right at 4 p.m., not far from the town of Pinch. Hail nearly 3″ in diameter was reported not far from Pinch at Capital High School. Base velocity, which shows the velocity of parcels in the atmosphere, indicated winds in excess of 60 mph between Big Chimney and just east of Pinch during the same period (top right). The probability of severe hail, shown in a percentage, was nearly 100% as the storm moved out of the capitol city, and struck the eastern Kanawha County towns of Pinch and Elkview (bottom left). The maximum indicated hail size on radar was around 2.50″ at 4 p.m. according to radar. Any estimated maximum hail size over 2″ is indicated in purple (bottom right).

A cross section of the storm about 1 mile southeast of Pinch at 4:02 p.m. indicated 65 dbz radar returns at 25,000 feet, which likely indicated a severe hail core in the supercell as it moved east. Very large hail occurred not far from this location.

Once the supercell moved east through Clay County and into Nicholas County, the storm began weakening significantly, and dissolved in Webster County. Trees were still reported down in Nicholas County in the Summersville area, but by that point, the supercell was in its decaying stage.

Tennis ball-sized hail fell in the Mink Shoals area of Kanawha County as a result of the storm. Capital High School saw baseball-sized hail (photo courtesy of the National Weather Service).